Compact infrared broadband source

ABSTRACT

A device for the generation of supercontinuum in infrared fiber with a compact light source comprising a microchip laser is launched directly into an infrared fiber without a nonlinear element. Light from the laser is beyond the two-photon absorption of the infrared fiber. The broadband output has a bandwidth greater than the input laser bandwidth by at least 100% and an emission wavelength range from 2 to 14 micrometers.

PRIORITY CLAIM

The present application is a divisional application of U.S. Pat. No.10,126,630 (U.S. application Ser. No. 15/699,013, filed on Sep. 8, 2017by Rafael R. Gattass et al., entitled “Compact Infrared BroadbandSource”), which was a divisional application of U.S. Pat. No. 9,785,033(U.S. application Ser. No. 14/608,473, filed on Jan. 29, 2015 by RafaelR. Gattass et al., entitled “Compact Infrared Broadband Source”), whichclaimed the benefit of U.S. Provisional Application No. 61/933,327,filed on Jan. 30, 2014 by Rafael R. Gattass et al., entitled “CompactInfrared Broadband Source.” The entire contents of all of theseapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to optical supercontinuum generation orbroadening of bandwidth of an optical signal whereby wavelength of thesignal is broadened between about 2 and 14 microns.

Description of the Prior Art

Nonlinear optical phenomena can be used to convert light from onewavelength to another, but it can also convert a narrow bandwidthwavelength source into a broadband source. The generation of a broadbandsource through a combination of nonlinear phenomena is typically calledsupercontinuum generation. In supercontinuum generation, pulses offemtoseconds (fs) to nanoseconds (ns) are spectrally broadened byvarious nonlinear processes, including self-phase modulation, stimulatedRaman scattering and four wave mixing, dependent on the pump temporalproperties and the dispersion slope of the fiber. While supercontinuumgeneration is possible by focusing a high intensity light into anonlinear medium, much broader bandwidths and significantly lowerthresholds are possible when the pump is coupled into an optical fiberwhere the guiding characteristics of the fiber allow the pump tointeract with the nonlinearities of the fiber materials over longlengths.

Among the various available high power laser pumps, microchip lasersources are compact, capable of pulse widths below 5 ns (typical valuesrange from 40 ps to 5 ns), and repetition rates from Hz to MHz. Modalprofile for these lasers is very good, usually being below M²<1.5.Multiple material systems allow for the development of microchip laserarchitectures with emission wavelength spanning visible to mid-IR. Suchlasers are usually based on rare-earth elements such as Nd, Yb, Er, Dy,Pr, Sm, Eu, Ho, and Tm but may also include Cr, Fe, and other transitionmetal ions. These active dopants are supported in a host that can be acrystalline material such as yttrium aluminum garnet (YAG), yttriumlithium fluoride (YLF), yttrium orthovanadate (YVO4), yttrium aluminumperovskite, potassium-gadolinium tungstate (KGW), yttrium scandiumgallium garnet (YSGG), ZnSe, and others; ceramic materials such aslutetium oxide, spinel, yttrium oxide, and others; glass materials suchas germanates, fluorides, ZBLAN, chalcogenides, tellurites, and others.Other examples include transition metal (TM²⁺, e.g., Cr²⁺ or Fe²⁺) dopedbinary (e.g. ZnSe, ZnS, CdSe, CdS, ZnTe) and ternary (e.g., CdMnTe,CdZnTe, ZnSSe) chalcogenide crystals and ceramics.

Microchip lasers are a unique class of laser systems with manyproperties distinct from those from other laser architectures such aslaser diode or fiber lasers. Of particular importance to the presentinvention are pulsed microchip lasers, as the peak power of thesesystems can be very high, easily exceeding kW peak powers in a packagewhose volume can be on the order of cm³. The high peak power avoids theneed for further amplification of these laser systems, the short lengthof the microchip laser provides a short-pulse without the need to resortto optical pulse modulation, external pulse shaping elements ornonlinearly induced pulse break-up such as modulation instability.

Compared to focusing into a nonlinear medium, optical fibers allow forlong interaction lengths through optical waveguiding. An optical fibercomprises a core surrounded by one or more claddings. Light travels inthe core and is confined by the index difference between the core andcladding. Microstructured fiber or photonic crystal fiber is a fiberwhereby the cladding (or claddings) comprises a geometric arrangement ofair holes in the cladding glass. Inhibit coupling fiber is a hollow corefiber whereby the density of light states is reduced but non-zero andthe modal overlap between the air guided mode and the substrate mode(cladding mode) is minimal, allowing light to be guided in the hollowmode with low loss.

Supercontinuum generation has been demonstrated in silica fiber in thevisible and near infrared. Unfortunately, transmission of the silicaglass matrix limits the supercontinuum generation to less than about 2μm. For supercontinuum generation in the infrared, alternatetechnologies and materials are needed.

Chalcogenide fiber is one technology capable of transmission well beyond2 μm. Chalcogenide fibers are fibers comprising the chalcogen elements,sulfur, selenium, and tellurium. Typically, other elements are added tostabilize the glass. Arsenic sulfide, As₂S₃, and arsenic selenideAs₂Se₃, germanium arsenic sulfide, germanium arsenic sulfide telluride,and germanium arsenic selenide are examples of chalcogenide glass.Chalcogenide fibers typically do not transmit well in the visible range.The use of high peak power pumps for supercontinuum generation in thesefibers risks damage from two-photon absorption, so pumps in thewavelength range greater than 1.5 m are typically used.

Many of the microchip lasers previously described are capable of laseremissions above 1.5 um, however sources with emissions below 1.5 um andfor those applications where power is preferred to remain within aspecified wavelength band, a nonlinear element can be used inconjunction with the laser to shift the color of the laser to a longerwavelength. Examples of nonlinear elements are bulk nonlinear materialwith sufficient transmission at the pump wavelength. Examples arenonlinear crystals such as lithium triborate (LBO), beta barium borate(BBO), zinc germanium phosphide (ZGP), potassium dihydrogen phosphate(KDP), silver thiogallate (AGS), silver selenogallate (AGSe), galliumselenide (GaSe), lithium indium sulfide (LiInS₂), lithium indiumselenide (LISe), and others. Alternatively, high-efficient conversion isalso possible with quasi-phase matched material such as periodicallypoled lithium niobate, periodically poled potassium titanyl phosphate,or periodically patterned gallium arsenide, and others. Besidesconversion in devices with high second order nonlinearity (χ⁽²⁾),conversion can be induced through Raman shifting as in the case of Ramanconverters. Examples of Raman converters can be in the form of agas-cell, an optical fiber or crystal.

For those alternatives for nonlinear conversion where second ordernonlinearity is used for the wavelength conversion, the presentinvention does not require the use of a cavity, ensuring a compact andstable laser source. The method focuses on wavelength conversion throughoptical parametric generation, not requiring a set of mirrors to form acavity. A single pass configuration for the optical parametricgeneration is preferred. Alternatively, a method where wavelengthconversion prior to coupling into the fiber occurs through opticalparametric amplification. Optical parametric amplification requires theuse of seed laser increasing the complexity of the system, however itcan be used to narrow the converted bandwidth, improve the mode orincrease the power conversion.

Many applications exist for bright broadband infrared sources beyondabout 2 μm. Of particular interest are light sources in the chemical andbiological “fingerprint region” from 3-12 jam for biological andchemical sensing and sources within the atmospheric transmission windowsfrom 2-5 μm and 8-12 μm for infrared countermeasures and certain radar(LIDAR) applications. Other applications for such sources includeinfrared illuminators and infrared sources for hardware-in-the-looptesting. Supercontinuum sources in the infrared would enable theseapplications. For these applications, the size and weight of the lightsource are of particular importance. In particular there is growinginterest in portable sources (weight on the order of 20 kg, dimensionson the order of 20 cm×20 cm×20 cm). Current inventions do not addressthe size and weight limitations currently needed.

Shaw (U.S. Pat. No. 7,133,590) teaches a method of generatingsupercontinuum in a chalcogenide fiber, either conventional core/cladfiber or microstructured photonic crystal fiber within the range of 2 to14 μm by launching pump light into a chalcogenide fiber whereby theinput pump light is broadened by several nonlinear mechanisms in saidfibers. However, the invention describes supercontinuum generation infibers wherein the pump light propagates at a wavelength that is in theanomalous or near-zero dispersion.

Islam (U.S. Pat. No. 7,519,253) teaches a system and method to generatesaid broadband supercontinuum in either chalcogenide, fluoride, ortellurite fiber with a pump light consisting of a short pulse laserdiode with wavelength of shorter than 2.5 μm and pulse width of at least100 ps with one or more optical amplifier chains and a nonlinear fiberwith anomalous dispersion at the diode wavelength that modulates thediode though modulation instability. In addition to the modulationinstability stage, the invention requires the use of an amplificationstage after the laser pump, increasing the weight and complexity of anydevice based on this invention. The invention does not teach how toovercome the challenges with the use of other pumps systems such asmicrochip lasers, and those whose wavelength lie in the normaldispersion regime of the fiber. It also requires the amplification ofthe pump signal to at least 500 W peak power in a second element such asa fiber amplifier.

Shaw (U.S. Pat. No. 7,809,030) teaches a method for converting light tothe infrared through the use of AsS chalcogenide fibers pumped by anoptical parametric oscillator. The invention does not disclose how toovercome the challenges with the use of other chalcogenide fibermaterials such as AsSe, and GaAsSeTe, as well as the challengesassociated with the use of nonlinear conversion without the use of acavity.

Shaw (U.S. patent application Ser. No. 13/742,563) teaches a method forgenerating supercontinuum light in the mid-infrared through the use of afiber based pump source. Although the invention does focus onpropagation in the normal dispersion regime, it does not address thechallenges involved in using a micro-optic packaged system or bulksystem for pumping a fiber within this regime.

Zayhowski (“Miniature sources of subnanosecond 1.4-4.3 μm pulses withhigh peak power,” in Advanced Solid State Lasers 34, TuA11 (2000),“Miniature gain-switched lasers,” in Advanced Solid-State Lasers 50, WA1(2001)) teach a method for fabricating compact miniature laser sourceswith high peak power and narrow bandwidths centered on wavelengthswithin the range of 1 to 4.3 μm. The cited work does not teach a methodfor generating broadband wavelength emission within this range or how toextend the range further into the infrared.

BRIEF SUMMARY OF THE INVENTION

The aforementioned problems are overcome in the present invention whichprovides a method and device for a compact light source based on amicrochip laser, a nonlinear optical element and a fiber-basedwavelength transmitter. The output of the source will have a bandwidthexceeding the input laser bandwidth by at least 100% and with anemission wavelength range within the range of 2 and 14 micrometers.

The method described above enables compact broadband infrared fibersource with high power and high brightness emission. Examples of thesize and weight of a compact microchip based system can be found in theliterature, the size of a microchip element, nonlinear element can be onthe order of 10 in³, the optical fiber and coupling do not add anysignificant weight (<100 g) and can serve to route the signal to anintended emission aperture. Such a source would have applications inspectroscopy, LIDAR, IRCM, laser surgery, and free space communications.

The device has advantages over other mid-IR supercontinuum sourcesdemonstrated. Source have been demonstrated in fluoride fiber, however,they have only been able to reach ˜4.3 μm using all fiber pumping.Sources have reached beyond 5 μm using short length of fluoride fiberand large bulky Ti:Sapphire based OPA pumps, however, these systems arenot compact and the average power was typically very low (<50 mW). Thesource described in this invention can be designed to operate anywherein the transparency range of the fiber by choosing the appropriate pump,nonlinear element and power. The fiber acts to extend that range ofwavelengths accessible by nonlinear conversion while simultaneouslybroadening the spectrum of the system. The choice of a microchip basedpump or a similarly compact laser pump (e.g. high power quantum cascadelaser) simplifies the number of elements in the pump laser system,reducing not only the size and weight of the system, but also reducingthe number of failure points for the system. The system described isscalable to multi-watt power in a micro-optics package.

The proposed architecture for the device and method have the advantageof allowing for the isolation of the electrical and thermal managementrequired for more complex systems (previously cited) from the opticallyactive components.

These and other features and advantages of the invention, as well as theinvention itself, will become better understood by reference to thefollowing detailed description, appended claims, and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of compact supercontinuum device used fordemonstration. L1-L4: collimation and focusing lenses. F: Long pass 2500nm filter. Detector indicates the fiber coupled scanning monochromator.The band around the PPLN indicates a temperature controlled oven.

FIG. 2 shows broadband light emission from chalcogenide fiber pumpedwith a compact microchip laser.

FIG. 3 shows a side view of sample geometry to be used in a method forgenerating broadband light (not to scale) including (A) pump laser suchas microchip laser (example sample dimensions 2 mm×2 mm, 1 mm long), (B)and (D) microlenses, (C) nonlinear element such as PPLN crystal (exampledimensions 10 mm×1 mm, 20 mm long), and (E) infrared fiber such as AsSefiber (example dimensions 10 um core, 200 um cladding, 2 m long).

FIG. 4 shows a side view of sample geometry to be used in a method forgenerating broadband light (not to scale) showing pump, nonlinearelement and fiber all mechanically bonded including (A) pump laser, (B)nonlinear element, and (C) infrared fiber.

FIG. 5 shows a side view of sample geometry to be used in a method forgenerating broadband light (not to scale) having a low-power thresholdbroadband source module with pump laser (A) coupled into waveguidesupported nonlinear element (B) such as waveguide PPLN chip, coupled toinfrared fiber (C).

FIG. 6 shows a side view of sample geometry to be used in a method forgenerating broadband light with optical parametric amplification as amain method for wavelength conversion in nonlinear element (not toscale) including (A) pump laser, (B) seed laser, (C) beam coupler, (D)nonlinear element, and (E) infrared fiber. Coupling between elementsmight require lenses depending on the beam sizes and geometries.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method and device for generation ofsupercontinuum in infrared fiber with a pump light comprising a laseroperating with wavelength of 1.5 μm or greater that can be wavelengthshifted though a nonlinear element and launched into infrared fiberwhereby the spectrum is broadened in the infrared fiber through variousnonlinear processes to generate a supercontinuum within the mid-IR from2 to 14 μm.

In one embodiment, a Nd:YAG microchip laser operating at 1.064 μm withpulse width of 700 ps and repetition rate of 20 kHz is used as a pumpfor optical parametric generation in a periodically poled lithiumniobate crystal. The crystal period is set such that the 1.064 μmgenerates a 1.45 μm pulse and a 3.82 μm pulse in a single passconfiguration (with no seed or cavity). The 3.82 μm pulse is coupledinto a selenide-based optical fiber of approximately 2 μm length, withan effective core diameter of 12 μm. The chalcogenide fiber broadens thelight by various nonlinear phenomena to a bandwidth between 3.65 and4.90 μm. FIG. 1 shows a schematic of the demonstration. FIG. 2 shows thespectrum of the generated supercontinuum.

A sample schematic of a device based on the method described herein isshown in FIG. 3. A narrowband pump source from a microchip laser coupledinto a nonlinear element through a lens. The pump light is converted totwo (or more) wavelengths in a nonlinear element. The longer wavelength(say λ₁) light is coupled to a non-linear fiber through another lens.The dispersion of the chalcogenide fiber can be normal, zero, oranomalous at the input λ₁ wavelength, and the generated broadband lightis emitted in the infrared within the range of 2 to 14 μm.

A variation of the sample schematic in FIG. 3 is presented in FIG. 4.Here the microchip laser, nonlinear element and fiber are bondedtogether either mechanically or optically with no need of imagingoptics.

A variation of the sample schematic in FIG. 3 is presented in FIG. 5.Here the nonlinear element also allows for waveguiding of the light, andis aligned such that the output of the nonlinear element is coupled intoan infrared fiber.

A waveguiding nonlinear element use in an architecture such as thatdescribed in FIG. 5 or the one in FIG. 3, could comprise a fiber basedRaman shifter or waveguide inscribed second order nonlinear element suchas a waveguide based periodically poled lithium niobate chip. Note thatneither of these elements requires that the dispersion of light at theinput wavelength be anomalous and do not base their wavelengthconversion on a physical mechanism called modulation instability. Theuse of a waveguide nonlinear element also allows for conversion of lightat very low peak powers, with efficiency >5% possible even for lightpowers well below 500 W.

The narrowband pump source can be a q-switched laser system, includingmicrochip lasers with emission from 1 to 5 μm such as but not restrictedto Nd:YAG lasers, Er:YAG lasers, Er:ZBLAN, as well as high power quantumcascade lasers (a wider list of materials has been presented in thebackground section). The nonlinear element need not be present if thepump source is sufficiently long wavelength as to avoid two-photonabsorption in the fiber. Here the nonlinear fiber can comprise anappropriately transparent material such as fluoride, tellurite,germanate, halide or chalcogenide glass.

Chalcogenide glass fibers suitable herein include fibers with outerdiameter (O.D.) typically in the range of 50-1000 μm, and more typicallyin the range of 100-500 μm. Core size is in the range of 1-100 μm indiameter, but typically range from smaller cores of about 1 μm indiameter to larger cores of about 50 μm in diameter. Generally speaking,the smaller the core the higher the energy density and the broader thebandwidth, for a given power. In order to keep light within the core,its refractive index is kept higher than that of the clad.

Examples of nonlinear elements supported by this method and devicepresented in this patent include nonlinear elements composed of aquasi-phase matched material such as periodically poled lithium niobate,periodically poled potassium titanyl phosphate, or periodicallypatterned gallium arsenide. Other nonlinear elements are also possibleas those experienced in the field would know, as long as there issufficient transmission at the pump wavelength through the nonlinearmaterial. Examples are nonlinear crystals such as lithium triborate(LBO), beta barium borate (BBO), zinc germanium phosphide (ZGP),potassium dihydrogen phosphate (KDP), silver thiogallate (AGS), silverselenogallate (AGSe), gallium selenide (GaSe), lithium indium sulfide(LiInS₂), lithium indium selenide (LISe). Additionally, the nonlinearelement can be based on a Raman converter. The Raman converter can be inthe form of a gas-cell, an optical fiber or crystal.

A method where by frequency conversion prior to coupling into the fiberoccurs through optical parametric generation, not requiring a set ofmirror to form a cavity. A single pass configuration for the opticalparametric generation is preferred. Alternatively, a method wherefrequency conversion prior to coupling into the fiber occurs throughoptical parametric amplification—where a seed is used to narrow theconverted bandwidth, improve the mode or increase the power conversion.One arrangement for the case of optical parametric amplification ispresented in FIG. 6. The power of the pump laser and a weaker seed laserare combined and coupled into a nonlinear element. The combination canoccur through a dichroic mirror, a polarization element, evanescentcoupler, interferometric waveguide combination or any other beamcombiner. The polarization of the seed laser is selected to maximize theenergy conversion from the pump laser to the new wavelength, and doesnot need to be the same as the pump. The effect of the polarization onthe conversion efficiency should be clear for those knowledgeable in theart, and will depend on the nonlinear element architecture used.

A method whereby the pump laser is selected to maximize the powertransfer to a Raman line or a cascade of Raman lines in an infraredfiber. The nonlinear element used after the pump would generate two newwavelengths with the energy spacing being close to or within the Ramangain of the fiber. One such embodiment would include the use of a pumplaser and nonlinear element to generate such that the power carried atthe pump wavelength λ_(p) would be efficiently converted to two newwavelengths λ₁ and λ₂ where the spacing of the wavelengths would bechosen such that (λ₁)⁻¹+(λ₂)⁻¹=Λ±dΛ, where Λ is the Raman gain peak forthe infrared fiber (in inverse wavenumbers) and dΛ represents thebandwidth of the gain. For example for As₂S₃, Λ would be 340 cm⁻¹ and dΛwould be 60 cm⁻¹. In this embodiment of the method, the power carried byboth λ₁ and λ₂ would be coupled into the infrared fiber. Nonlinearpropagation in the fiber together with Raman gain would lead tobroadening of the pump colors from the two narrow bands around λ₁ and λ₂to a broadband source. The Raman process would be efficiently excited asλ₂ would seed Raman scattering from λ₁.

The following examples illustrate these embodiments.

Example 1

An Er:YAG microchip laser operating with a pulse width of greater than10 ps and less than 2 ns and wavelength around 2.8 μm converted in aperiodically poled gallium arsenide crystal to generate a longwavelength laser pulse at 5 um. The pulses are launched into a solidcore clad As—Se fiber where a supercontinuum is generated from 2 to 14μm through a combination of Raman conversion and self phase modulation.

Example 2

The system described in Example 1 where no nonlinear element is used andthe laser is coupled directly into a chalcogenide fiber such as As₂S₃fiber. The pulses are launched into a solid core clad As—S fiber where asupercontinuum is generated from ˜2.8 to 6 μm through a combination ofRaman conversion and self-phase modulation.

Example 3

A quantum cascade laser with peak power levels exceeding 1 W or averagepower continuous wave power exceeding 10 mW is coupled directly into aphotonic crystal fiber of AsSe. The effective diameter of the AsSe fiberis designed to magnify the nonlinear parameter and reduce the requiredpower level for supercontinuum generation to below 10 W.

Example 4

A device whereas the pump laser is transition metal doped chalcogenidecrystal (or ceramic) q-switched laser such as Cr:ZnSe, operating around2.4 μm with pulse width below 2 ns. A nonlinear crystal element such asZGP which converts the wavelength of the pump into the mid-infrared orfar-infrared and is coupled into a solid core AsSe fiber.

Example 5

A system composed of a compact laser pump source, a nonlinear elementand an infrared fiber. The laser pump source (either a microchip laserbased on one of the previously described compositions or a quantumcascade laser with a peak power greater than 10 W) operating at arepetition rate from CW to MHz, a nonlinear element for shifting thepump power to a wavelength which will not have significant two-photonabsorption in a fiber. Example of such elements are quasi-phase matchedcrystals as those previously described, Raman shifters, and nonlinearcrystals such as those previously described. An infrared fiber (such asthose of material composition previously described) wherein the incidentwavelength propagates in normal or anomalous regime, and broadens to atleast 100% of the incident bandwidth.

Example 6

A system composed of a compact laser pump source and an infrared fiber.The laser pump source (either a microchip laser based on one of thepreviously described compositions or a quantum cascade laser with a peakpower greater than 10 W) operating at a repetition rate from CW to MHz,without a nonlinear element for shifting the pump as the pump wavelengthalready did not display two-photon absorption in the fiber. The infraredfiber (such as those of material composition previously described)wherein the incident wavelength propagates in normal or anomalousregime, and broadens to at least 100% of the incident bandwidth.

The above descriptions are those of the preferred embodiments of theinvention. Various modifications and variations are possible in light ofthe above teachings without departing from the spirit and broaderaspects of the invention. It is therefore to be understood that theclaimed invention may be practiced otherwise than as specificallydescribed. Any references to claim elements in the singular, forexample, using the articles “a,” “an,” “the,” or “said,” is not to beconstrued as limiting the element to the singular.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. A device for generating a supercontinuum in aninfrared fiber with a light source, comprising: a pulsed microchip laserhaving an input laser bandwidth, wherein said pulsed microchip laser hasa pulse duration between 40 ps and 5 ns; and an infrared fiber, whereinsaid infrared fiber is a chalcogenide glass fiber, wherein said pulsedmicrochip laser is launched directly into said infrared fiber without anonlinear element, and wherein light from said pulsed microchip laser isbeyond the two-photon absorption of said infrared fiber; and a broadbandoutput having a bandwidth greater than said input laser bandwidth by atleast 100% and an emission wavelength range from 2 to 14 micrometers. 2.The device of claim 1, wherein said pulsed microchip laser comprises anoptically active element Nd, Yb, Er, Dy, Pr, Sm, Eu, Ho, Tm, atransition metal ion Cr or Fe, or any combination thereof.
 3. The deviceof claim 1, wherein said pulsed microchip laser has a repetition ratebetween 100 Hz and 100 MHz.
 4. The device of claim 1, wherein saidpulsed microchip laser has a pulse duration between 500 ps and 2 ns anda repetition rate between 10 kHz and 10 MHz.
 5. The device of claim 1,wherein said device weighs 20 kg or less and has dimensions of 20 cm×20cm×20 cm or less.
 6. A device for generating a supercontinuum in aninfrared fiber with a light source, comprising: a pulsed microchip laserhaving an input laser bandwidth, wherein said pulsed microchip laser hasa pulse duration between 40 ps and 5 ns; and an infrared fiber, whereinsaid infrared fiber is a chalcogenide glass fiber, wherein said pulsedmicrochip laser is launched directly into said infrared fiber without anonlinear element, and wherein light from said pulsed microchip laser isbeyond the two-photon absorption of said infrared fiber; and a broadbandoutput having a bandwidth greater than said input laser bandwidth by atleast 100% and an emission wavelength range from 2.8 to 6 micrometers.7. The device of claim 6, wherein said pulsed microchip laser comprisesan optically active element Nd, Yb, Er, Dy, Pr, Sm, Eu, Ho, Tm, atransition metal ion Cr or Fe, or any combination thereof.
 8. The deviceof claim 6, wherein said pulsed microchip laser has a repetition ratebetween 100 Hz and 100 MHz.
 9. The device of claim 6, wherein saidpulsed microchip laser has a pulse duration between 500 ps and 2 ns anda repetition rate between 10 kHz and 10 MHz.
 10. The device of claim 6,wherein said device weighs 20 kg or less and has dimensions of 20 cm×20cm×20 cm or less.